Oxygen enhanced combustion in industrial processes

Abstract

The present invention relates to a system for carrying out oxygen-enhanced combustion in an industrial process wherein the industrial process, an oxygen supply system or a source of oxygen, a heat recovery network, and an alternative Rankine cycle system based on a working fluid other than steam are integrated to achieve improved throughput and efficiency, and a method for oxygen-enhanced combustion in an industrial process using said system. Examples of industrial processes include cement production, steel reheat applications, glass production, aluminum and copper melting, as well as any industrial process that uses process heater, furnaces where combustion is carried out using an oxidant stream with oxygen content higher’ than that in ambient air and up to 100%.

Description

RELATED APPLICATION[0001]This application claims the priority to U.S. Provisional Application No. 60 / 833,258, filed on Jul. 25, 2006, the entire contents of which are incorporated by reference herein.TECHNICAL FIELD[0002]The present invention generally relates to the field of cogeneration of power and heat, and particularly to recover heat lost to ambient air using oxygen enhanced combustion.BACKGROUND OF INVENTION[0003]Oxygen enhanced combustion is utilized in industrialized furnace applications to increase throughput and has additional advantages such as lower emissions, improved flame stability and heat transfer. Although increased thermal efficiency is claimed for processes that use oxy-fueled combustion, making use of the unavoidably generated waste heat remains a challenge. Unlike air-fired processes, where the excess thermal energies from the flue gases are used to preheat the air for combustion, in oxygen enhanced combustion, the hazards of handling hot oxygen-enriched strea...

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Benefits of technology

[0010]Also, the invention seeks to integrate in an efficient manner the utilization of the power generated with the oxygen supply system, or any demand of electrical power within the industrial process considered. The power output of the alternative Rankine cycle could be in the form of electricity, and the alternative turbine of the alternative Rankine cycle can be directly coupled to one of the power consuming devices through a shaft or through a motor / generator assembly for reducing equipment cost associated with generating electricity and distributing it to different devices. Having a motor / generator assembly will provide flexibility in operation.

[0011]Use of oxygen enhanced combustion increases the availability of low-grade heat sources, which could become valuable opportunities for power generation. However, steam power generating systems are less efficient when heat source is available at temperatures lower than 400° C., due to lack of economic viability caused by poor achievable efficiency typical to steam processes at such low temperature. Generation of electrical energy by alternative Rankine cycles (including organic Rankine cycles), which can make use of low temperature heat, represents a feasible alternative. In addition, using a working fluid other than steam has other advantages, such as low mechanical stressing of the turbine as a result of the low speed of the turbine impeller, direct drive of the electrical generator without any reduction gear unit, no erosion of the turbine blades due to absence of moisture in the vapor, and thus, simple maintenance and operation and longer service life of the plant.

[0012]Oxygen enhanced combustion is utilized in many industrial applications to increase throughput, which decreases the need for building new plants and thus minimizing capital investment. In addition, the power generated from heat sources produced as a consequence of oxy-fuel combustion reduces the net demand of electricity of the oxygen supply system. Therefore, the present invention helps to lower the cost of power and / or lower the cost of oxygen for oxy-fuel conversion. The oxygen demand for a typical cement plant for a 25% throughput increase is 650-1450 tpd, whilst the power generated can range between 4-7 MW.

Problems solved by technology

However, steam power generating systems are less efficient when heat source is available at temperatures lower than 400° C., due to lack of economic viability caused by poor achievable efficiency typical to steam processes at such low temperature.

In addition, the power generated from heat sources produced as a consequence of oxy-fuel combustion reduces the net demand of electricity of the oxygen supply system.

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